when doing your time travel calculations and including the expansion of the universe with appropriate accuracy to not miss the bus.
Otherwise this might only be useful to calculate the total worldwide debt :)
(Btw. the Sanyo ICC-804D had 16 digit precision back in 1971 - but no nifty functions besides 4 basic operations and on/off)

Quote:
The forensics is not meant to highlight the accuracy of a certain calculator but to identify identical algorithms and/or calculator chips.

True for this level of precision we're talking about here. In general, however, the forensics sheds some light on the reliability of calculation results. Think of error propagation in iterative computations ...

The WP-34s displays 9.00000000003, that is, the internal result is rounded to the number of digits of the display. HP used to round the result and truncate it to the number of digits in the display at the end of each operation. Thus, the HP-42S displays 8.99999864267. HP's method makes sense because the results of the operations are coherent to the actual figures of the operands the user has access to (by examining their mantissas, for instance).

I assume the 34s is a 16-digit device, but the calculations are carried out with extra guard digits, otherwise it wouldn't achieve the correct rounded 16-digit result we see. Another reason to get the WP-34s as soon it's available :-)